Media captionMark Mardell reports on President Obama's decision to go for a pause

President Obama surprised Washington with his announcement. Many expected the missiles would be in the air by now. Instead the attack has been put on hold for at least 10 days.

It may not impress those who habitually accuse him of dithering, but at least members of Congress are, this time, unlikely to complain.

He is likely to win the vote, going by the public expressions of members of Congress in the last few days.

Clearly he thinks he will. But then so did his mate, David Cameron.

He is trapped within his own red lines and perhaps the need to send a signal to Iran and North Korea.

The humiliation of the British prime minister played directly into his decision. The shock made some advisers even more averse to letting Congress have a say.

But its real impact was perverse. It led to the recall, according to White House insiders.

In the past, Britain has been accused of being America's poodle. This time MPs clamped their teeth into the seat of Mr Obama's trousers, ripping a hole in his argument of the obvious virtue of action.

The forcible removal of America's oldest enemy (John Kerry pointedly referred to the French on Friday as "our oldest ally - they were helping the Americans fight the British from 1778-83) from the world stage meant Obama needed some more moral support for his case.

Protesters in the US who start arguing, "But even Britain…" can be answered with, "But Congress has…"

Presuming they do vote in favour, that is.

Some will say this shows Obama is weak. Rather, it shows his hand is weak.

He was elected to end America's wars, and in reaction to the fallout of the invasion of Iraq.

Many of his own supporters want him to focus on what he calls "nation-building at home".

But he is trapped within his own red lines and, perhaps, the need to send a signal to Iran and North Korea.

A recent poll indicated 80% of Americans thought Congress should vote before any military action.

Taking action that is unpopular, with an uncertain international coalition and domestic reluctance, is not a strong position to be in.

But it is sensible to make sure the responsibility for unpopular action is shared with other politicians, as Caesar's assassins knew.

It is also canny for domestic reasons to keep a very sour Congress sweet. Some might even argue in a democracy it is the right thing to do.